If you haven't had wines from the Ahr be sure to check out the great insights from Dustin Chabert, Jeremy Eubanks, Blake Leja, Alex Ring, Mark Guillaudeu and inderpal singh last week.
This week: TDN in Riesling
What does the acronym stand for? How does it manifest in the glass? What causes it? Are there particular regions that display more than others?
Different sources disagree on its ultimate cause, but in riesling at least it seems that the aromatic precursors to it require a certain amount of sun exposure in the grapes. That said, recent studies out of Adelaide have shown that TDN is present as a byproduct of yeast in virtually all white wine, but only rises above detection threshold in certain varieties and regions (Semillon, Germany, etc.).
Then you also have the rebels like Marc Kreydenweiss who insist that TDN is in fact a bacterial flaw that consumers have been educated to accept (like the skunking of Stella) rather than winemakers trained to eradicate. In spite of it being considered by many the signature aroma of the riesling grape there still seems to be surprisingly little funding and ongoing research toward a fuller understanding of its ultimate causes.